1. Field of Invention
The present invention relates to an organic electroluminescent white light source and a method for manufacturing the same. In particular, the present invention relates to an organic electroluminescent white light source useful for a backlight of a liquid crystal display device to be used for a computer display, portable terminal and portable phone, and a method for manufacturing the same.
2. Description of Related Art
Cold-cathode tubes and inorganic LEDs are used for the backlight of the liquid crystal display device to be used for the computer display, portable terminal and portable phone. In conjunction with the recent trend of miniaturization and low power consumption of the computer, portable terminal and portable phone, developments of thinner and low power-consuming white backlight sources are desired.
Developments of thin-type organic electroluminescence (abbreviated as EL hereinafter) elements that consume a small power have been also aggressively developed in recent years. Particularly, the elements that emit blue, green, yellow and orange colors have been extensively investigated, and their luminance and service life have reached a practical level. Luminance and service life of a white organic EL element manufactured by a vacuum deposition method have been also improved.
Application of these organic EL elements to the white backlight have been also aggressively studied. Japanese Unexamined Patent Application Publication No. 3-187192 discloses an invention in which organic EL elements are arranged as a mosaic pattern corresponding to color pixels on the liquid display device. Japanese Unexamined Patent Application Publication No. 10-39791 discloses an invention in which the pixel area ratio among the red, blue and green colors is controlled for white balance using the same addressing voltage among the color pixels in the organic EL display device.
A special material should be used in luminous layers manufactured by the conventional method for obtaining a white color in the organic EL element, in addition to difficult problems for manufacturing the luminous layers. Sufficient characteristics have not been realized in the organic EL elements of the type requiring to form the white luminous layers by coating polymer materials.
Accordingly, one object of the present invention is to at least provide a structure that allows a balanced white color to be readily obtained by either a vacuum deposition method or a coating method, and a method for manufacturing the same.
One exemplary embodiment of the present invention provides an organic EL white light source having a laminated structure which may include a common anode, luminous layers and a common cathode. The luminous layer may include a plurality of luminous material layers emitting different colors with each other to provide plural luminous regions, and a white light is obtained by color mixing by allowing the plural luminous layers to light by simultaneously applying a voltage to the plural luminous layers.
A white light can be obtained using luminous materials that emit colors other than the white color. Consequently, the EL element can be addressed with a low addressing voltage with a high luminance and reliability. The construction also enables cost-down of the power source unit since white light is emitted using a single addressing power source.
In the organic EL white light source according to another exemplary embodiment in relation to the above-described embodiment of the present invention, the planar configuration of each luminous region corresponding to each of the plural luminous layers is a circle or an ellipsoid.
The luminous layer is more uniformly formed when the luminous material is formed by a coating method, in particular by an ink-jet method when the planar configuration of the luminous region is a circle or an ellipsoid.
In the organic EL white light source according to another exemplary embodiment in relation to the above-described embodiment of the present invention, each luminous region corresponding to each of the plural luminous layers is regularly arranged with a periodic repeating unit.
The luminous colors from respective luminous regions are mixed and emitted as a white color in the arrangement as described above.
In the organic luminous EL white light source according to another exemplary embodiment in relation to the above-described embodiment of the present invention, each luminous region is regularly arranged with a periodic repeating unit along a first direction, and a linear arrangement of luminous regions having the same color is formed along a second direction perpendicular to the first direction.
The luminous colors from respective luminous regions are mixed with each other and the mixed light is emitted as a white color in the arrangement as described above, thereby enabling throughput for forming the luminous layer by an ink-jet method.
In the organic EL white light source according to another exemplary embodiment in relation to the above-described embodiment of the present invention, the area ratio of the luminous region in each luminous layer is adjusted so that a white color is obtained.
A white light is emitted by addressing all the luminous layers with the same voltage in the construction as described above.
In the organic EL white light source according to another exemplary embodiment in relation to the above-described embodiment of the present invention, each luminous layer in the plural luminous layers is addressed so as to minimize the addressing voltage as a sum of consumed electric power of each luminous layer.
The construction as described above allows power consumption of the light source for addressing each luminous layer to be decreased.
In the organic EL white light source according to another exemplary embodiment in relation to the above-described embodiment of the present invention, the plural luminous colors may include two colors.
The process cost for forming each luminous layer is decreased since only two times of deposition steps are required for patterning in the construction as described above.
In the organic EL white light source according to another exemplary embodiment in relation to the above-described embodiment of the present invention, the plural luminous colors may include three colors.
A balanced white light source may be realized by the construction as described above.
In the organic EL white light source according to another exemplary embodiment in relation to the above-described embodiment of the present invention, a light diffusion plate is placed on the luminous surface of the light source.
The shape of each luminous region may be blurred in the construction as described above, thereby enabling a more uniform planar white emission to be obtained.
In the organic EL white light source according to another exemplary embodiment in relation to the above-described embodiment of the present invention, a light diffusing substrate is used for the substrate for the light source.
The construction as described above can eliminate the need of disposing the light diffusion plate as a separate plate, thereby enabling to provide simplicity in structure and to reduce the production cost.
Another exemplary embodiment of the present invention provides an organic electroluminescent white light source having a laminated structure which may include an anodes, luminous layers and a cathode on a substrate, and the plural luminous layers are disposed on the substrate. A plurality of division walls for dividing a plurality of luminous layers are provided on the substrate, and the luminous regions are distributed with a space apart with each other by disposing at least the luminous layer in each divided region. A white light is obtained by allowing each luminous layer to light by simultaneously applying a voltage to the luminous layer in each luminous region.
A white planar light having such characteristics as uniform and stable luminance can be obtained using luminous materials with colors other than a white color in the construction as described above.
The organic EL white light source according to another exemplary embodiment in relation to the above-described embodiment of the present invention may include a common anode for the plural luminous layers.
The organic EL white light source according to another exemplary embodiment in relation to the above-described embodiment of the present invention may include a common cathode for the plural luminous layers.
A stable white light may be obtained using a simple construction as described above.
In the organic EL white light source according to another exemplary embodiment in relation to the above-described embodiments of the present invention, the luminous layer is formed by an ink-jet method.
A uniform luminous layer may be obtained only in a specified region of the luminous layer in the construction as described above, enabling a white light source having good characteristics to be realized.
In the organic EL white light source according to another exemplary embodiment in relation to the above-described embodiment of the present invention, the planar configuration of the luminous region is a circle or an ellipsoid.
A uniform luminous layer may be obtained particularly when the luminous layer is formed using the ink-jet method in the construction as described above.
The organic EL white light source according to another exemplary embodiment in relation to the above-described embodiment may further include an auxiliary electrode provided on the surface of the common anode for enhancing electrical characteristics of the common anode.
Electrical characteristics such as uniform surface potential of the common anode may be enhanced by the construction as described above, thereby reducing irregular light emission.
Another exemplary embodiment of the present invention provides a method for manufacturing an organic EL white light source having a laminated structure which may include a common anode, luminous layers and a common cathode. The luminous layer may include a plurality of luminous material layers emitting different colors with each other. A white light is obtained by color mixing by simultaneously applying a voltage to and lighting the plural luminous layers. The luminous layer corresponding to each of the plural luminous layers emitting each color is formed by an ink-jet method.
The white light source may be readily manufactured with a low manufacturing cost, since no positioning is required in disposing the luminous layers and expensive EL materials are not wasted.
Another exemplary embodiment of the present invention provides a method for manufacturing an organic electroluminescent white light source having a laminated structure which may include a common anode, luminous layers and a common cathode. The luminous layer may include a plurality of luminous material layers emitting different colors with each other, and a white color is obtained by color mixing by simultaneously applying a voltage on and lighting the plural luminous layers. The luminous layer corresponding to each of the plural luminous regions emitting each color is formed by a vacuum deposition method.
The element as described above can emit a white light by providing uniform luminous layers in the white light source.
Another exemplary embodiment of the present invention provides a method for manufacturing an organic electroluminescent white light source having a laminated structure which may include a common anode, luminous layers and a common cathode. The luminous layer may include a plurality of luminous material layers emitting different colors with each other, and a white color is obtained by color mixing by simultaneously applying a voltage on and lighting the plural luminous layers. The luminous layer corresponding to each of the plural luminous layers emitting each color is formed by a printing method.
The present invention provides a process for manufacturing the white light source having good patterns with a low manufacturing cost.
In the method for manufacturing the organic EL white light source according to another exemplary embodiment in relation to the above-described embodiment of the present invention, a plurality of luminous materials having different luminous colors with each other are used in forming the luminous layer and, after coating one kind of a luminous material on the entire surface of a substrate as a host material, other luminous materials are coated as dotted dopant materials on the host material coated on the entire surface of the substrate.
The division walls among the luminous layers may be omitted in the construction as described above.
In the method for manufacturing the organic EL white light source according to another exemplary embodiment in relation to the above-described embodiment of the present invention, plural kinds of luminous materials having different luminous colors with each other are used as the luminous layer on which each kind of luminous materials is coated with no gaps among the luminous materials.
The division walls among the luminous layers may be omitted in the construction as described above.
In the method for manufacturing the organic EL white light source according to another exemplary embodiment in relation to the above-described embodiment, a plural kinds of luminous materials having similar aging characteristics are used for forming the plural luminous layers.
A white light as a synthesized luminous light may be always obtained even when the luminous light changes by aging in the construction as described above.